The present invention is generally related to apparatus and method for curing coating materials, and specifically to apparatus and method for simultaneously irradiating curable coatings on multiple optical fibers, thread or yarn fibers or wire-like elements.
Optical fibers, such as are used to transmit light in is various applications, including communications, typically are coated with one or more polymeric layers which are designed to protect the optical fibers from moisture and abrasion, to reduce microbending losses, and to allow easier handling of the fiber.
In a typical method of coating an optical fiber, a liquid photocurable polymeric material is applied to the surface of the fiber and it is then cured by irradiating the coated fiber with radiant energy, as for example, ultraviolet rays.
Attempts have been made in the prior art to improve the efficiency of the coating and curing process by techniques such as modifying the polymer composition and/or the coating method and selecting optimum wavelengths of the curing radiation. One area in which it has appeared that improvements can be made in the curing process is in more efficient use of the radiant energy which is used to cure the polymer.
Based on the use of a full-elliptical reflector with a tubular UV (or visible or infrared) light source at one focus and the high-intensity zone of illumination at the other, it is difficult to pass a number of fibers through the same zone at the same time. The primary difficulty is in the carrying and handling devices for each fiber, which prevents these devices from being placed close together. The coating dies or heads for coloring or coating of fiber on the xe2x80x9cupstreamxe2x80x9d side (where the fiber will have wet coating or ink on it) prevent the fibers from being spaced closely.
It is an object of the present invention to provide an apparatus and method for passing multiple fibers through a small zone of high-intensity radiant energy, thereby making more efficient use of the existing irradiator.
In summary, the present invention provides an apparatus for passing multiple fibers having curable coating thereon through a high intensity curing zone, comprising an irradiator having a curing zone; a transparent tube enclosing the curing zone; a plurality of coating dies disposed upstream of the irradiator to coat the fibers; and a plurality of take-up mechanisms disposed downstream of the irradiator to guide the fibers through the curing zone. The coating dies and the take-up mechanisms are rotatably displaced relative to each other about a longitudinal axis through the centerline of the curing zone so that the fibers at an intermediate location between the coating dies and the take-up mechanisms define a cylindrical volume having a diameter less than the diameter of the tube so that the multiple fibers can pass simultaneously through the tube.
The present invention also provides a method for passing multiple fibers having curable coating thereon through a high intensity curing zone, comprising:
a) providing a curing zone having a diameter;
b) providing a plurality of feed guides upstream of said curing zone to guide the fibers through the curing zone
c) providing a plurality of take-up guides downstream of said curing zone to take-up the fibers passing through the curing zone; and
d) rotating the upstream and the downstream guides relative to each other about a longitudinal axis through the centerline of the curing zone so that the fibers at an intermediate location between the upstream and downstream guides define a cylindrical volume having a diameter less than the diameter of the curing zone.
These and other objects of the present invention will become apparent from the following detailed description.